(defun Info-file-supports-index-cookies (&optional file)
"Return non-nil value if FILE supports Info index cookies.
Info index cookies were first introduced in 4.7, and all later
-makeinfo versions output them in index nodes, so we can reply
+makeinfo versions output them in index nodes, so we can rely
solely on the makeinfo version. This function caches the information
in `Info-file-supports-index-cookies-list'."
(or file (setq file Info-current-file))